This invention relates to a sealing member used in an analyzer, particularly in a portable analyzer or an on-line analyzer, by which sealing member it is possible to achieve a tight seal between a stationary sample and the analyzer in order to perform the analysis in a desired gas atmosphere.
When analyzing a sample of conductive material, such as metal, using optical emission analysis, an electric discharge is created between the sample and the electrode of the probe. In an apparatus that uses optical emission analysis, the sample is pressed against the probe. In the thus-formed measuring chamber, an argon atmosphere is normally used during the measurement. Any oxygen that is present as an impurity in the chamber atmosphere impairs the accuracy of the result of the analysis. A metal-to-metal pressure contact exists between the analyzer probe and the sample. This kind of a contact can provide a satisfactory seal in the case of a stationary analyzer, but, for example in a portable or on-line analyzer, it has not been possible to create a satisfactory seal by pressure contact between the sample and the probe.
Attempts have been made to improve the seal between a sample and the probe of an optical emission analyzer by, for example, positioning a silicon mat between the sample and the probe. Further, in the apparatus according to the DE patent application 2833324 an elastic O-ring is used in the seal. The use of a sealing ring is also described in the EP patent application 174374 and in the GB patent 1490991. However, the one-part elastic sealing ring described in the references mentioned above does not necessarily give a sufficient seal, because the gas components in the external atmosphere, as oxygen, can be absorbed through this kind of seal. In a stationary optical emission analyzer designed for laboratory use the seal can also be manufactured of a ceramic material, when the electrical connection between the probe and the sample is achieved otherwise than by pressure contact between the probe and the seal. This arrangement is, however, inconvenient for a portable or on-line analyzer.